Detector Array

Detector characteristics are given in this section. Note that the GMOS-South detectors have been upgraded in 14B. Note also that the telescope optics are now silver-coated, reducing the system throughput in the blue.

The GMOS-S detectors were upgraded to the new Hamamatsu CCDs, improving red sensitivity, and including an upgraded detector controller. The GMOS-North original EEV detectors were replaced with e2v deep depletion devices in October 2011, improving sensitivity in the blue and greatly improving / extending sensitivity to longer wavelengths (this upgrade is intended to be followed afterward with a second upgrade featuring a new focal plane array populated with Hamamatsu devices).

The recommended detector read-out configuration for all GMOS-N observations using the e2v DD detectors is

slow read

low gain

6 amplifiers

The original intent was to use the three best amplifiers, giving the lowest read-noise. This was the case for the original EEV detectors; however, for the new e2v DD detectors a recabling enacted to reduce spurious noise has yielded the 3 amplifiers mode unavailable. All GMOS-N data taken since November 22 has utilized 6-amp mode.

It is recommended
not to use the fast read mode unless read-out speed is essential for the
science goals of the program, i.e. time resolved
observations.
High gain is recommended only for programs that target very bright objects.

For the Hamamatsu detectors, the default detector read-out configuration is

slow read

low gain

12 amplifiers

The six-amplifier mode is not supported (three-amplifier mode is not available for these CCDs). Fast read-out speed is available for time resolved observations and high gain for observations of very bright objects.